Oregon Bonsai uses fish fertilizer supplemented with kelp meal year round (and an occasional dose of Miracle Grow), purchased in bulk, but here is a great retail source. I have used the fish and the all purpose, both deodorized, so the smell isn't too bad. I would recommend the all purpose, as it has fish, blood, bone, yadda, yadda... It is all organic, doesn't smell too bad, and is pretty cost effective - something like $5 for 3lbs of the stuff. Pile the pellets and they will make a nice little glob of moldy gunk in no time - and a couple of applications will last the year.
I don't use pellet fish now, as my Yellow Lab eats the pellets like chocolate, so I use the liquid fish/kelp in the second link.
http://www.lillymiller.com/alaska.html#dryallpurp
http://www.neptunesharvest.com/
Don't forget to seek out your local farm supply - you too can buy the same items in bulk 50# bags and save lotsa $.